Refacturing Config

[sweinbach]

Is your feature request related to a problem? Please describe.
Trying to get neox to run, one notices complexity in the way config is provided to different components. Refacturing may increase readability and testability of code.

Describe the solution you'd like

• One data class (may be still global) including separate data classes by purpose (model, deepspeed)
• data class can update values from .yml files
• data class can return formatted output (e.g. for deepspeed call)
• data class can print config values
• data class can do other stuff currently implemented in megatron/arguments and megatron/config_monser.py